The present invention relates to a mobile communication terminal device that supports both noncontact proximity communication and wireless communication longer in communication distance than noncontact proximity communication and includes a security controller utilized in security processing in these types of communication and to a technology effectively applicable to, for example, a cellular phone having authentication and settlement functions.
A mobile terminal device having a noncontact proximity communication function refers to a device originally intended to be mainly used for any other purpose (cellular phone mainly intended for a telephone call function or the like) with noncontact authentication and settlement functions added thereto. Single-function card terminal devices dedicated to noncontact authentication and settlement functions basically do not use a battery. They receive a carrier wave (carrier) generated by an oppositely placed reader/writer and operates using its electromagnetic field power. When a mobile terminal device is additionally provided with its noncontact authentication and settlement functions, it consumes more power than card terminal devices. As a result, it cannot carry out its functions by supply of power by electromagnetic field transfer and must eventually use a battery. The reason for this is as follows: unlike card terminal devices, mobile terminal devices are made multifunctional so that a security controller carrying out security processing for noncontact authentication and settlement can be used also in mobile communication processing; and for this purpose, the performance of the CPU of the security controller and further the capacity of a storage device are increased and this increases power consumption.
The mobile terminal device functions on power supplied from a battery. Because of use for the principal purpose of the device, however, the power from the battery is consumed and it may get itself cornered in a situation in which it cannot carry out its functions for the principal purpose. In the mobile terminal device, power supply capability is estimated by monitoring the value of the output voltage of the battery. When the estimated value becomes equal to or lower than a certain voltage value, it is determined that the device has been brought into an unusable state and the functions for the principal purpose are stopped. However, the noncontact authentication and settlement functions do not consume so much power as the principal purpose. Therefore, even in such a state of power supply capability that the functions for the principal purpose cannot be carried out, there are the following cases: cases where the noncontact authentication and settlement functions can be carried out until the value is reduced to the next predetermined voltage value.
However, the noncontact authentication and settlement functions equipped in a mobile terminal device consume more power than those of single-function card terminal devices dedicated to noncontact authentication and settlement functions. Even though it seems to be operable according to the state of its battery self-discharging, the period for which it is operable is very short. There is not a high possibility that its noncontact authentication and settlement functions can be used during a period for which these functions can be carried out after the stop of the functions for the principal purpose. As a result, there is a high possibility that noncontact authentication or settlement cannot be carried out, either unless the supplying capability of the battery is restored. A mobile terminal device containing electronic information for the user's commuter pass will be taken as an example. If its noncontact authentication functions cannot be used because of battery remaining capacity shortage, the terminal device cannot operate as a commuter pass. In this case, the user must pay a fare in cash though he/she carries the pass unless the battery is recharged to bring the terminal device into a usable state.
Patent Document 1 describes a technology for reducing the power consumption of a cellular phone provided with, in addition to a telephone function, a noncontact IC card function part for carrying out a noncontact authentication function and a settlement function. According to this, to lengthen the life of a battery, battery power is supplied to the noncontact IC card function part when electromagnetic field power becomes short.    [Patent Document 1] Japanese Unexamined Patent Publication No. 2006-60700